Originally Posted by Vegas300SD

Hello, Jack from Vegas here. Just purchased an amazingly clean '81 300SD with 190,000 miles on it. Nearly every service record was available, drove it the 300+ miles from Phoenix to Vegas with minimal drama.

There is a few things I want to pick this site's brains on, but right now the most glaring problem occured yesterday.

Coming to a stop the brake pedal went to the floor!!!

Have some mechanical apptitude but have forgotten how to diagnose a power booster or a master cylinder.........

Because it acts like it's not holding line pressure, I'm leaning toward the MC...or should I say I'm hoping it's the MC.

I seem to remember a booster going out on an old truck years back and the pedal was rock hard...

Thanks in advance for all suggestions.